Workpiece processing device and method

ABSTRACT

A workpiece processing device includes a workpiece supporting unit configured to support a workpiece so that the workpiece is rotatable around a first axis parallel to a central axis of the workpiece, a cutting unit having a blade configured to cut a surface of the workpiece, a detecting unit configured to calculate a position of a vertex of the surface in a direction along a second axis which is perpendicular to the first axis and parallel to the blade, and a control unit configured to control the workpiece supporting unit so that a cutting position on the surface is located at a vertex in the direction along the second axis, and relatively move the workpiece supporting unit and the cutting unit so that an incision direction of the blade is on a plane defined by the central axis and the cutting position, thereby forming a groove at the cutting position.

This application is a Divisional of U.S. application Ser. No.17/187,538, filed Feb. 26, 2021, which is a Continuation of U.S.application Ser. No. 17/270,388, filed Feb. 22, 2021, which is theNational Phase of PCT International Application PCT/JP2020/008941, filedMar. 3, 2020, which claims priority under 35 U.S.C. 119(a) to JapanesePatent Application No. 2019-040657, filed Mar. 6, 2019, Japanese PatentApplication No. 2020-035650, filed Mar. 3, 2020 and Japanese PatentApplication No. 2020-035651, filed Mar. 3, 2020. Each of the aboveapplications is hereby expressly incorporated by reference, in itsentirety, into the present application.

TECHNICAL FIELD

The presently disclosed subject matter relates to workpiece processingdevice and method, and relates to workpiece processing device and methodfor processing a cylindrical-shape workpiece.

BACKGROUND ART

When a cylindrical-shape workpiece is processed, the workpiece issupported so as to be rotatable around a workpiece rotation axis, andground by using a working tool such as a grindstone. For example, PatentLiterature 1 discloses a grinder for grinding a cylindrical-shapeworkpiece by bringing a working tool into contact with a cylindricalsurface or end surface of the workpiece (a surface orthogonal to theworkpiece rotation axis) while causing the cylindrical-shape workpieceto rotate around the workpiece rotation axis.

CITATION LIST Patent Literature

{PTL 1} Japanese Patent Application Laid-Open No. 2010-105128

SUMMARY OF THE INVENTION Technical Problem

There is a case where the surface of a cylindrical-shape workpiece issubjected to processing of forming a groove extending in the lengthdirection (central axis direction) of the cylinder (hereinafter referredto as grooving). For example, when a convex type ultrasonic probe iscreated, a layer of a piezoelectric element (for example, lead zirconatetitanate) having a driving electrode is formed on the surface of acylindrical-shape packing material, and the grooving is performed on thelayer of the piezoelectric element to cut the layer of the piezoelectricelement into a plurality of elements, thereby creating an ultrasonicprobe in which the plurality of elements for transmitting and receivingultrasonic waves are formed on the surface of the packing material.

When the grooving as described above is performed, a workpiece is firstrotatably attached to a workpiece supporting unit. Then, the workpieceis rotated to be positioned so that a processing position of theworkpiece (a target position for forming a groove, hereinafter referredto as a cutting position) and a blade face each other, and the bladeperforms incision toward the central axis of the workpiece to form onegroove. Repetition of this positioning and cutting makes it possible toform a groove at each cutting position on the surface of the workpiece.

In the grooving as described above, it is required that the incisiondirection of the blade is perpendicular to the surface of the workpiece.In other words, the incision direction of the blade and the radialdirection of the workpiece (the normal direction of the surface(cylindrical surface) of the workpiece) are required to match eachother. If the incision direction of the blade is inclined with respectto the radial direction of the workpiece in the ultrasonic probe, theprocessing accuracy of the plurality of elements is deteriorated, andcharacteristics such as transmission and reception characteristics ofultrasonic waves are varied among the elements. Variations incharacteristics among the elements may cause noise in ultrasonic images.

In order to make the incision direction of the blade and the radialdirection of the workpiece match each other, it is considered that thecentral axis of the cylindrical-shape workpiece and the workpiecerotation axis are made to match each other when the workpiece isattached to the workpiece supporting unit. However, when the workpieceattaching accuracy (mechanical accuracy) cannot be sufficiently secured,there is a problem that the center axis of the workpiece and theworkpiece rotation axis deviate from each other, resulting indeterioration of the processing accuracy of the grooving.

Further, when the central axis of the workpiece and the rotation axis ofthe workpiece are made to match each other, the size of a workpiecewhich can be processed is restricted by, for example, the distancebetween the workpiece rotation axis and the blade, movable ranges of theworkpiece supporting unit and the blade, etc. In order to process alarge-size workpiece, it is necessary to secure the distance between theworkpiece rotation axis and the blade and the movable ranges of theworkpiece supporting unit and the blade, which causes a problem that thesize of the device and the cost increase.

The presently disclosed subject matter has been made in view of suchcircumstances, and has an object to provide workpiece processing deviceand method that can perform, with high accuracy, grooving on thesurfaces of workpieces which have cylindrical-shape surfaces and variousshapes and sizes.

Solution to Problem

In order to solve the foregoing problem, a workpiece processing deviceaccording to a first aspect of the presently disclosed subject matter isa work processing device for processing a workpiece having acylindrical-shape surface, which comprises: a workpiece supporting unitfor supporting the workpiece so that the workpiece is rotatable around afirst axis parallel to a central axis of the workpiece; a cutting unithaving a blade for cutting a surface of the workpiece supported by theworkpiece supporting unit; a detecting unit for calculating a positionof a vertex of the surface of the workpiece in a direction along asecond axis which is perpendicular to the first axis and parallel to theblade; and a control unit for controlling the workpiece supporting unitso that a cutting position on the surface of the workpiece is located ata vertex in the direction along the second axis, and relatively movingthe workpiece supporting unit and the cutting unit so that an incisiondirection of the blade is on a plane defined by the central axis of theworkpiece and the cutting position on the surface of the workpiece,thereby forming a groove at the cutting position.

According to the first aspect, even when the central axis of theworkpiece and the first axis (workpiece rotation axis) do not match eachother in grooving on the surface of the cylindrical-shape workpiece, itis possible to perform grooving with high accuracy because the incisiondirection of the blade can be kept perpendicular to the surface of theworkpiece. Further, according to the first aspect, since it isunnecessary that the central axis of the workpiece and the rotation axisof the workpiece match each other, the attachment posture of theworkpiece can be adjusted according to the shape and size of theworkpiece, and the workpiece processing device can be applied toworkpieces having various sizes.

A workpiece processing device according to a second aspect of thepresently disclosed subject matter further comprises, in the firstaspect, a calculating unit for calculating positions of at least threevertices in the direction along the second axis at at least threerotation positions w % ben the workpiece is rotated around the firstaxis, calculating a locus of a center of the workpiece based on thepositions of the at least three vertices when the workpiece is rotatedaround the first axis, and calculating the cutting position based on aposition of the center of the workpiece and a radius of the workpiece.

A workpiece processing device according to a third aspect of thepresently disclosed subject matter is configured in the second aspect sothat the detecting unit calculates a cutting reference position on thesurface of the workpiece when the cutting reference position is locatedat the vertex in the direction along the second axis, and thecalculating unit calculates the position of the center of the workpieceand the radius of the workpiece based on calculation results of thepositions of the at least three vertices and the cutting referenceposition.

A workpiece processing device according to a fourth aspect of thepresently disclosed subject matter further comprises, in any of thefirst to third aspects, a camera capable of imaging the surface of theworkpiece, wherein the detecting unit detects a vertex of the surface ofthe workpiece based on an image captured by moving the camera in adirection along a third axis perpendicular to the first axis while thecamera is focused on a position farther than the vertex of theworkpiece.

A workpiece processing device according to a fifth aspect of thepresently disclosed subject matter further comprises, in any of thefirst to fourth aspects, a sensor unit for measuring a height positionof the cutting position on the surface of the workpiece, wherein thecontrol unit adjusts an incision depth of the blade based on ameasurement result of the height position of the cutting position.

A workpiece processing device according to a sixth aspect of thepresently disclosed subject matter is a workpiece processing device forprocessing a workpiece having an outwardly-convex curved-surface-shapesurface, comprises: a workpiece supporting unit for supporting theworkpiece so that the workpiece is rotatable around a first axis; acutting unit having a blade for cutting the surface of the workpiecesupported by the workpiece supporting unit; a sensor unit for measuringthe surface of the workpiece; a calculating unit for calculating asurface shape of the workpiece on a plane perpendicular to the firstaxis based on a measurement result of the surface of the workpiece; anda control unit for relatively moving the workpiece supporting unit andthe cutting unit based on the surface shape of the workpiece calculatedby the calculating unit, thereby forming one or more grooves on thesurface of the workpiece.

A workpiece processing device according to a seventh aspect of thepresently disclosed subject matter is configured in the sixth aspect sothat the calculating unit calculates a cutting position at which thegroove is formed on the surface of the workpiece based on the surfaceshape of the workpiece and an interval of the grooves to be formed onthe surface of the workpiece, and the control unit relatively moves theworkpiece supporting unit and the cutting unit based on the cuttingposition, thereby forming the groove at the cutting position.

A workpiece processing device according to an eighth aspect of thepresently disclosed subject matter further comprises, in the sixth orseventh aspect, a detecting unit for calculating a position of a vertexof the surface of the workpiece in a direction along a second axis whichis perpendicular to the first axis and parallel to the blade, whereinthe detecting unit detects positions of vertices at a plurality ofrotation positions to which the workpiece is rotated around the firstaxis from a reference rotation position of the workpiece bypredetermined rotation angles, and the calculating unit calculatespositions of a plurality of points on the surface of the workpiece atthe reference rotation position based on the positions of the verticesat the plurality of rotation positions and the rotation angles from thereference rotation positions, and calculates a surface shape functionrepresenting a surface shape of the workpiece based on the positions ofthe plurality of points.

A workpiece processing device according to a ninth aspect of thepresently disclosed subject matter is a workpiece processing device forprocessing a workpiece having an outwardly-convex curved-surface-shapesurface, comprises: a workpiece supporting unit for supporting theworkpiece so that the workpiece is rotatable around a first axis; acutting unit having a blade for cutting the surface of the workpiecesupported by the workpiece supporting unit; a sensor unit for measuringthe surface of the workpiece, a calculating unit for calculating asurface shape of the workpiece on a plane perpendicular to the firstaxis based on a measurement result of the surface of the workpiece; anda control unit for rotating the workpiece around the first axis based onthe surface shape of the workpiece and a cutting position at which agroove is formed on the surface of the workpiece so that the cuttingposition matches a vertex in a direction along a second axis which isperpendicular to the first axis and parallel to the blade, andrelatively moving the workpiece supporting unit and the cutting unit,thereby forming a groove at the cutting position.

A workpiece processing device according to a tenth aspect of thepresently disclosed subject matter is configured in the ninth aspect sothat the calculating unit calculates a normal line to the surface of theworkpiece at the cutting position based on the surface shape of theworkpiece, and the control unit rotates the workpiece around the firstaxis so that the normal line is parallel to a direction along a secondaxis which is perpendicular to the first axis and parallel to the blade,and relatively moves the workpiece supporting unit and the cutting unit,thereby forming a groove at the cutting position.

A workpiece processing device according to an eleventh aspect of thepresently disclosed subject matter is configured in the ninth aspect sothat the calculating unit calculates a tangent line to the surface ofthe workpiece at the cutting position based on the surface shape of theworkpiece, and the control unit rotates the workpiece around the firstaxis so that the tangent line is perpendicular to a direction along asecond axis which is perpendicular to the first axis and parallel to theblade, and relatively moves the workpiece supporting unit and thecutting unit, thereby forming a groove at the cutting position.

A workpiece processing device according to a twelfth aspect of thepresently disclosed subject matter further comprises, in any of thefirst to eleventh aspects, an adjusting mechanism for adjusting a fixingsurface on which the workpiece is fixed in the workpiece supportingunit, and a cut-feeding direction of the blade.

A workpiece processing method according to a thirteenth aspect of thepresently disclosed subject matter is a workpiece processing method forprocessing a workpiece having a cylindrical-shape surface, whichcomprises: a step of supporting the workpiece on a workpiece supportingunit so that the workpiece is rotatable around a first axis parallel toa central axis of the workpiece; a step of calculating a position of avertex of the surface of the workpiece in a direction along a secondaxis which is perpendicular to the first axis and parallel to a blade;and a step of controlling the workpiece supporting unit so that acutting position on the surface of the workpiece is located at a vertexin the direction along the second axis, and relatively moving theworkpiece supporting unit and the blade so that an incision direction ofthe blade is on a plane defined by the central axis of the workpiece andthe cutting position on the surface of the workpiece, thereby forming agroove at the cutting position.

A workpiece processing method according to a fourteenth aspect of thepresently disclosed subject matter is a workpiece processing method forprocessing a workpiece having an outwardly-convex curved-surface-shapesurface, comprises: a step of supporting the workpiece on a workpiecesupporting unit so that the workpiece is rotatable around a first axis;a step of measuring the surface of the workpiece by a sensor unit andcalculating a surface shape of the workpiece on a plane perpendicular tothe first axis based on a measurement result of the surface of theworkpiece; and a step of relatively moving the workpiece supporting unitand the blade based on the surface shape of the workpiece, therebyforming a groove on the surface of the workpiece.

A workpiece processing method according to a fifteenth aspect of thepresently disclosed subject matter is a workpiece processing method forprocessing a workpiece having an outwardly-convex curved-surface-shapesurface, which comprises: a step of supporting the workpiece on aworkpiece supporting unit so that the workpiece is rotatable around afirst axis; a step of measuring the surface of the workpiece by a sensorunit; a step of calculating a surface shape of the workpiece on a planeperpendicular to the first axis based on a measurement result of thesurface of the workpiece; and a step of rotating the workpiece aroundthe first axis based on the surface shape of the workpiece and a cuttingposition at which a groove is formed on the surface of the workpiece sothat the cutting position matches a vertex in a direction along a secondaxis which is perpendicular to the first axis and parallel to the blade,and relatively moving the workpiece supporting unit and the cuttingunit, thereby forming a groove at the cutting position.

Advantageous Effects of the Invention

According to the presently disclosed subject matter, when grooving isperformed on the surface of a cylindrical-shape workpiece, it ispossible to form a groove with high accuracy without making the centralaxis of the workpiece and the workpiece rotation axis match each other.Further, according to the presently disclosed subject matter, since itis not necessary to make the central axis of the workpiece and theworkpiece rotation axis match each other, the attachment posture of theworkpiece can be adjusted according to the shape and size of theworkpiece, which makes it possible to process workpieces having varioussizes. Further, according to the presently disclosed subject matter,regardless of whether the surface of the workpiece has a cylindricalshape or non-cylindrical shape, the incision position and depth of theblade can be adjusted with high accuracy by calculating the surfaceshape.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a workpiece processing device according toan embodiment of the presently disclosed subject matter.

FIG. 2 is a diagram showing another example of the workpiece processingdevice.

FIG. 3 is a perspective view showing a workpiece after grooving.

FIG. 4 is a diagram for illustrating a procedure of grooving.

FIG. 5 is a diagram for illustrating the procedure of grooving.

FIG. 6 is a diagram for illustrating the procedure of grooving.

FIG. 7 is a flowchart showing a workpiece processing method according toan embodiment of the presently disclosed subject matter.

FIG. 8 is a diagram for illustrating a procedure for detecting a vertexof the workpiece.

FIG. 9 is a diagram showing an example in which the surface shape of theworkpiece is not a cylindrical shape.

FIG. 10 is a diagram for illustrating a procedure of grooving for anoutwardly-convex curved-surface-shape workpiece.

FIG. 11 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 12 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 13 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 14 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 15 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 16 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 17 is a diagram for illustrating the procedure of grooving for theoutwardly-convex curved-surface-shape workpiece.

FIG. 18 is a flowchart showing a workpiece processing method accordingto an embodiment of the presently disclosed subject matter.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of workpiece processing device and methodaccording to the presently disclosed subject matter will be describedwith reference to the accompanying drawings.

[Workpiece Processing Device]

First, a workpiece processing device according to an embodiment of thepresently disclosed subject matter will be described with reference toFIG. 1, and (A) and (B) portions of FIG. 1 are a front view and a sideview of the workpiece processing device, respectively. Here, thefollowing description will be made by using a three-dimensionalrectangular coordinate system. The workpiece rotation axis (R-axis,first axis) is assumed to be parallel to an X-axis.

As illustrated in FIG. 1, the workpiece processing device 1 includes acontrol device 10, an X drive unit 20X, a Y drive unit 20Y, a Z driveunit 20Z, an R drive unit 20R, a cutting unit 22, a blade 24, a sensorunit 26, a workpiece supporting unit 28 and a workpiece table 30. In the(A) portion of FIG. 1, the control device 10 and the like are omittedfor simplification of the drawings.

The workpiece table 30 can be moved in an X direction by the X driveunit 20X including a motor, a ball screw and the like. The workpiecesupporting unit 28 is provided on the upper surface of the workpiecetable 30. A rotary table 28R is attached to the workpiece supportingunit 28. The rotary table 28R is rotatable around the workpiece rotationaxis (R-axis) by the R drive unit 20R including the motor and the like.The rotary table 28R includes a mechanism for fixing a workpiece W (forexample, a clamp mechanism). The above configuration enables theworkpiece W to rotate around the workpiece rotation axis (R-axis) andslide in the X direction while the workpiece W is fixed and supported bythe rotary table 28R.

The cutting unit (cutting part) 22 is movable in Y and Z directions viaa Y table and a Z table (not illustrated). The Y table is provided on aside surface of a Y base (not illustrated). The Y table is movable inthe Y direction by the Y drive unit 20Y including a motor, a ball screwand the like. A Z table (not illustrated) is attached to the Y table.The Z table is movable in the Z direction by the Z drive unit 20Zincluding a motor, a ball screw and the like.

The cutting unit 22 is fixed to the Z table. The blade 24 is attached tothe cutting unit 22. The blade 24 is a disk-shaped cutting blade, whichcan be rotated by a spindle motor (not illustrated). The blade 24 isheld in parallel to a ZX plane. As the blade 24 is used anelectrodeposition blade obtained by electrodepositing diamond abrasivegrains or CBN (Cubic form of Boron Nitride) abrasive grains with nickel,a resin blade obtained by bonding diamond abrasive grains or CBN (Cubicform of Boron Nitride) abrasive grains with resin, or the like. Theblade 24 can be moved in the Y direction by the Y drive unit 20Y, andalso can perform incision-feeding in the Z direction by the Z drive unit20Z.

The cutting unit 22 is provided with the sensor unit 26. The sensor unit26 includes a displacement sensor for measuring the distance to eachpoint on the surface W_(S) of the workpiece W. As the displacementsensor may be used, for example, a laser displacement sensor, an opticalor contact type displacement sensor, a TOF (Time of Flight) camera, orthe like.

Further, the sensor unit 26 includes an imaging device. The imagingdevice includes a microscope, a camera, and the like, and it images thesurface W_(S) of the workpiece W in order to perform alignment of theworkpiece W and evaluation of the processing state of the workpiece W.For example, an area sensor camera can be used as the camera.

The above configuration makes it possible to perform grooving on thesurface W_(S) of the workpiece W while rotating the workpiece W havingthe cylindrical-shape surface W_(S) around the rotation axis R foralignment.

Note that in the present embodiment, the workpiece table 30 is allowedto move in the X direction and the cutting unit 22 is allowed to move inthe Y and Z directions, but the moving directions of the workpiece table30 and the cutting unit 22 are not limited to these directions. Forexample, the workpiece table 30 may move in the Y and Z directions, andthe cutting unit 22 may move in the Z and X directions. In other words,the workpiece table 30 and the cutting unit 22 may be relatively movablealong the X, Y and Z directions.

Further, the workpiece processing device 1 may include an adjustingmechanism for adjusting a fixing surface on which the workpiece W isfixed on the rotary table 28R and the cutting direction of the workpieceW (the cutting feeding direction of the blade 24, X-axis). A manual orautomatic tilting stage mechanism 32 for tilting the workpiece W betweenthe workpiece W and the rotary table 28R may be used as the adjustingmechanism as illustrated in FIG. 2. Furthermore, as the adjustingmechanism may be used, for example, a mechanism for manually orautomatically rotating the workpiece supporting unit 28 around an axis(for example, the Y-axis or the Z-axis) perpendicular to the X-axis(R-axis) of the workpiece processing device 1. As a result, the cuttingfeeding direction of the blade 24 for the workpiece W and the X-axis(R-axis) of the workpiece processing device 1 can be made parallel toeach other.

In the present embodiment, the sensor unit 26 is provided in the cuttingunit 22 so as to be movable integrally with the cutting unit 22, but thesensor unit 26 and the cutting unit 22 may be movable separately fromeach other.

Next, a control system of the workpiece processing device 1 will bedescribed. The control device 10 controls the operation of each part ofthe workpiece processing device 1. The control device 10 can beimplemented by a general-purpose computer such as a personal computer ora microcomputer.

The control device 10 includes CPU (Central Processing Unit), ROM (ReadOnly Memory), RAM (Random Access Memory), a storage device (for example,a hard disk or the like), etc. In the control device 10, variousprograms such as a control program stored in the ROM are expanded in theRAM, and the programs expanded in the RAM are executed by the CPU toimplement the function of each unit of the control device 10.

As illustrated in FIG. 1, the control device 10 functions as a controlunit 12, a detecting unit 14, and a calculating unit 16.

The control unit 12 accepts an operation input from an operator via aninput/output unit 18 to control each unit of the control device 10, andcontrols the operation of the X drive unit 20X, the Y drive unit 20Y,the Z drive unit 20Z, and the R drive unit 20R.

The input/output unit 18 includes an operation member (for example, akeyboard, a pointing device, etc.) and a display unit for inputtingoperations.

The detecting unit 14 acquires data of a measurement result of thesurface W_(S) of the workpiece W from the displacement sensor of thesensor unit 26, and calculates the distance to the surface W_(S) of theworkpiece W. Further, the detecting unit 14 can calculate the height ateach position on the surface W_(S) of the workpiece W, and calculate thecoordinate of a vertex (a point having the maximum Z coordinate) in theZ-axis (second axis) direction of the workpiece W.

The calculating unit 16 calculates a correction circle C describedlater, the coordinate of a processing position (cutting position), etc.based on the vertex of the surface W_(S) of the workpiece W.

When grooving is performed on a plate-shaped workpiece W having acylindrical-shape surface W_(S) as illustrated in FIG. 3, the controlunit 12 controls the Y drive unit 20Y and the R drive unit 20R toperform alignment between the cutting position of the surface W_(S) ofthe workpiece W calculated by the calculating unit 16 and the blade 24.Further, the control unit 12 controls the X drive unit 20X to performcut-feeding in the X direction of the workpiece table 30 whilecontrolling the Z drive unit 20Z to perform incision-feeding in the Zdirection of the blade 24. As a result, as illustrated in FIG. 3,grooves G each having a predetermined depth extending toward the centerW_(C) of the cylindrical surface of the workpiece W are formed on thecylindrical-shape surface W_(S) of the workpiece W.

[Specific Example of Grooving]

Next, a procedure of grooving will be described with reference to FIGS.4 to 6. FIGS. 4 to 6 are diagrams for illustrating the procedure ofgrooving.

In the following description, a case where the grooves G are formed atangular intervals of δ in the circumferential direction of the surfaceW_(S) of the workpiece W will be described. Further, FIGS. 4 to 6 showthe workpiece W which is simplified in a fan shape connecting thesurface W_(S) and the center of the workpiece W. Further, the positionof the workpiece rotation axis (R-axis) is set to an origin (Y,Z)=(0,0).

First, the workpiece W having the cylindrical-shape surface W_(S) isattached to the rotary table 28R to calculate a correction circle C1 tobe used for alignment of the cutting position of the workpiece W. In thepresent embodiment, when the workpiece W is attached to the rotary table28R, the central axis of the workpiece W and the workpiece rotation axis(R-axis) only need to be parallel to each other, and are not required tomatch each other.

When the correction circle C1 is calculated, as illustrated in FIG. 4,the workpiece W is rotated around the R-axis to determine thecoordinates of vertices of the workpiece W (points having maximum Zcoordinates) at at least three rotation positions. When the coordinateof the vertex of the workpiece W at each rotation position isdetermined, the control unit 12 controls the Y drive unit 20Y to scanthe surface W_(S) of the workpiece W by using the displacement sensor ofthe sensor unit 26 and measures the distance from the displacementsensor to the surface W_(S) of the workpiece W at each scanning positionon the surface W_(S) of the workpiece W.

The detecting unit 14 calculates the Z coordinate of each scanningposition from data of the distance from the displacement sensor to thesurface W_(S) of the workpiece W at each scanning position. Further, thedetecting unit 14 calculates the shape of the surface W_(S) of theworkpiece W at each scanning position, and calculates the coordinates ofthe vertex having the maximum Z coordinate on the surface W_(S) of theworkpiece W. In the example illustrated in FIG. 4, the coordinates ofvertices P1, P2 and P3 of the workpiece W at three rotation positionsW1, W2 and W3 are designated by (Y1, Z1), (Y2, Z2) and (Y3, Z3),respectively.

The calculating unit 16 calculates the correction circle C1 which is acircle (a circumscribed circle of a triangle formed by three points P1,P2, and P3) passing through the three points P1 (Y1, Z1), P2 (Y2, Z2),and P3 (Y3, Z3). The correction circle C1 is a locus of the vertices ofthe workpiece W when the workpiece W is rotated around the R-axis. Thecalculating unit 16 determines the intersection point of perpendicularbisectors of line segments connecting respective two of the three pointsP1, P2, and P3 as the center of the correction circle C1. Further, thecalculating unit 16 calculates the distance between the center of thecorrection circle C1 and any of the three points P1, P2, and P3 as theradius Rc of the correction circle C1.

Here, when the central axis of the workpiece W and the R-axis match eachother, the following calculation is not performed, the blade 24 isarranged just above the R-axis, that is, in parallel to a plane of Y=0,the workpiece W is rotated around the R-axis by each angle δ to performalignment so that the cutting position is set to the position of Y=0,and then cutting is performed. As a result, a groove G having apredetermined depth extending toward the center W_(C) of the cylindricalsurface of the workpiece W can be formed on the cylindrical-shapesurface W_(S) of the workpiece W.

On the other hand, when the center W_(C) of the cylindrical-shapesurface W_(S) of the workpiece W and the R-axis do not match each other(separate from each other) as illustrated in FIG. 4, the center of thecorrection circle C1 does not match the R-axis. In this case, thefollowing calculation is performed, and the alignment between the blade24 and the cutting position is performed.

As illustrated in FIG. 5, at least one alignment mark M1 indicating areference for the cutting position (cutting reference position) isformed on the surface W_(S) of the workpiece W. When the center W_(C) ofthe cylindrical surface of the workpiece W and the R-axis do not matcheach other, the control unit 12 first controls the R drive unit 20R todrive the rotary table 28R so that the alignment mark M1 is located atthe vertex of the workpiece W. Hereinafter, the rotation position wherethe alignment mark M1 is located at the vertex of the workpiece W isdefined as W4.

Note that, in the example illustrated in FIG. 5, it is assumed that thealignment mark M1 is formed on a symmetrical axis of line symmetry ofthe workpiece W in order to simplify the subsequent calculation, but theformation position of the alignment mark M1 is not limited to thisposition.

Further, it is not essential to form the alignment mark M1 on thesurface W_(S) of the workpiece W. For example, the intersection pointbetween the surface W_(S) of the workpiece W and the symmetrical axis,or a central portion or end portion or the like of a cylindrical portionof the surface W_(S) of the workpiece W may be automatically set as thecutting reference position, or the cutting reference position may bemanually set by the operator.

The calculating unit 16 calculates the Y coordinate of the alignmentmark M1, that is, a deviation amount d in the Y direction of thealignment mark M1 with respect to the R-axis from the position of thealignment mark M1 at the vertex of the workpiece W detected by using theimaging device of the sensor unit 26. At this time, an intersectionpoint P4 between a correction circle C0 having a radius Rc centered onthe R-axis and a straight line Y=d becomes the position of the centerW_(C) of the workpiece W. In other words, the correction circle C0matches the locus of the center W_(C) of the workpiece W when the rotarytable 28R is rotated.

Next, the calculating unit 16 calculates, from the equation (1), anangle (hereinafter referred to deviation angle θ) at which a linesegment connecting the R-axis (origin (Y, Z)=(0,0)) and the position P4at the center of the workpiece intersects the Z-axis.

θ=arcsin(d/Rc)  (1)

The control unit 12 measures the distance from the displacement sensorto the alignment mark M1 by using the sensor unit 26. The detecting unit14 calculates the Z coordinate of the alignment mark M1, that is, theheight h from the data of the distance from the displacement sensor tothe alignment mark M1. Then, the calculating unit 16 calculates theradius r of the workpiece W by the equation (2).

r=h−Rc·cos θ  (2)

Next, the calculating unit 16 determines the center coordinate (Y4, Z4)of the workpiece W at the rotation position W4 by the equations (3) and(4).

Y4=d  (3)

Z4=h−r  (4)

After detecting the alignment mark M1, the control unit 12 controls theX drive unit 20X and the Y drive unit 20Y to move the blade 24 justabove the cutting reference position where the alignment mark M1 isformed. Then, the control unit 12 controls the Z drive unit 20Z and theX drive unit 20X to perform cutting at the cutting reference position.At this time, the incision direction of the blade 24 is perpendicular tothe surface W_(S) of the workpiece W. In other words, the incisiondirection of the blade 24 is on a plane defined by the central axis ofthe workpiece W and the cutting reference position of the surface W_(S)of the workpiece W. As a result, a groove G having a predetermined depthextending toward the center W_(C) of the cylindrical surface of theworkpiece W is formed at the cutting reference position.

Next, a case where grooving is performed at a cutting position which isrotated by an angle δ with respect to the cutting reference positionwill be described. Furthermore, for convenience of illustration, theangle S is illustrated to be exaggerated as compared with the actualinterval in the grooving in FIG. 6.

First, as illustrated in FIG. 6, the control unit 12 controls the Rdrive unit 20R to rotate the rotary table 28R by an angle of δ. Therotation position of the workpiece at this time is designated by W5.

The calculating unit 16 calculates the coordinate (Y5, Z5) of a positionP5 of the center W_(C) of the workpiece W at the rotation position W5 bythe equations (5) and (6).

Y5=Y4·cos δ−Z4·sin δ  (5)

Z5=Y4·sin δ+Z4·cos δ  (6)

At the rotation position W5, the cutting position is a vertex P6 of theworkpiece W just above the point P5 of the center W_(C) of the workpieceW. The calculating unit 16 determines the coordinate (Y6, Z6) of thecutting position P6 by the equations (7) and (8).

Y6=Y5  (7)

Z6=Z5+r  (8)

The control unit 12 controls the Y drive unit 20Y and the Z drive unit20Z based on the coordinate (Y6, Z6) of the cutting position P6 tocontrol the alignment between the cutting position P6 and the blade 24and the cutting depth. As a result, a groove G having a predetermineddepth extending toward the center W_(C) of the cylindrical surface ofthe workpiece W is formed at the cutting position which is away from thecutting reference position by an angle δ in the circumferentialdirection.

Subsequently, the workpiece W is rotated by an angle S, and the positionof the center W_(C) of the workpiece W and the cutting position arecalculated to perform alignment for each rotation position of theworkpiece W. Further, grooves G are likewise formed in a region on theleft side of the drawing with respect to the alignment mark M1. As aresult, as illustrated in FIG. 3, grooves G having a predetermined depthextending toward the center W_(C) of the cylindrical surface of theworkpiece W are formed on the surface W_(S) of the workpiece W at theintervals of the angle S.

According to the present embodiment, when the workpiece W is attached tothe rotary table 28R of the workpiece supporting unit 28, it is possibleto control the position of the workpiece W so that the cutting positionis set to the vertex of the workpiece W without making the central axisof the workpiece W and the workpiece rotation axis (R-axis) match eachother. As a result, grooving can be performed perpendicularly to thesurface W_(S) of the workpiece W, so that the grooving can be performedwith high accuracy.

Further, according to the present embodiment, since it is not necessaryto make the central axis of the workpiece W and the R-axis match eachother, the degree of freedom in the position and posture when theworkpiece W is fixed to the rotary table 28R is enhanced. Therefore,even in the case of a large-size workpiece or an elongated workpiece,the workpiece W can be attached so as to be fit in a space between theblade 24 and the R-axis by adjusting the attachment position and postureof the workpiece W according to the size and shape of the workpiece W.

Note that the interval S between the grooves G is constant in thepresent embodiment, but even when the interval between the grooves G isnot constant, the grooving can be performed in the same procedure asdescribed above.

Further, in the present embodiment, the interval between the grooves Gis defined by the angle δ, but it may be determined by the distance inthe circumferential direction of the workpiece W. In this case, thegrooving can be performed in the same procedure as described above byusing the radius r of the workpiece W and converting the distance in thecircumferential direction of the workpiece W into the rotation angle ofthe workpiece W.

[Workpiece Processing Method]

Next, a workpiece processing method (grooving method) according to thepresent embodiment will be described with reference to FIG. 7.

First, a workpiece W having a cylindrical-shape surface W_(S) is carriedinto the workpiece processing device 1, and fixed to the rotary table28R (step S10).

Next, the control unit 12 controls the R drive unit 20R to rotate theworkpiece W, and scans the surface W_(S) of the workpiece W at at leastthree rotation positions (W1 to W3 in FIG. 4) by using the displacementsensor of the sensor unit 26. The detecting unit 14 calculates thecoordinates of vertices of the workpiece W (P1 to P3 in FIG. 4) at atleast three rotation positions by using the data of a measurement resultobtained by the displacement sensor (step S12).

Next, the calculating unit 16 calculates the radius Rc of the correctioncircle C1 corresponding to the locus of the vertices of the workpiece Wfrom the coordinates of at least the three vertices of the workpiece W(step S14).

Next, the control unit 12 rotates the workpiece W so that the cuttingreference position on which the alignment mark M1 is formed becomes avertex of the workpiece W (step S16, the rotation position W4 in FIG.5). Then, the detecting unit 14 detects the vertex (cutting referenceposition) of the workpiece W at the rotation position W4, and calculatesthe deviation amount d in the Y-direction and the height h of the vertexof the workpiece W (step S18). Further, the calculating unit 16calculates the coordinate of the position P4 of the center W_(C) of theworkpiece W at the rotation position W4 and the radius r of theworkpiece W (step S20).

Next, the control unit 12 controls the Y drive unit 20Y and the Z driveunit 20Z to perform the alignment between the blade 24 and the cuttingreference position of the workpiece W. Then, the control unit 12controls the X drive unit 20X to perform the cut-feeding in the Xdirection of the workpiece table 30 while controlling the Z drive unit20Z to perform the incision-feeding in the Z direction of the blade 24,thereby performing cutting at the cutting reference position by theblade 24 (step S22).

Next, the control unit 12 controls the R drive unit 20R to rotate theworkpiece W so that a next cutting position becomes the vertex of theworkpiece W (step S24; rotation position W5 in FIG. 6). Then, thecalculating unit 16 calculates the coordinates of the position P5 of thecenter W_(C) of the workpiece W and the cutting position P6 at therotation position W5 (step S26).

Next, the control unit 12 controls the Y drive unit 20Y and the Z driveunit 20Z based on the coordinate of the cutting position P6 to performthe alignment between the blade 24 and the cutting reference position ofthe workpiece W. Then, the control unit 12 controls the X drive unit 20Xto perform the cut-feeding in the X direction of the workpiece table 30while controlling the Z drive unit 20Z to perform the incision-feedingin the Z direction of the blade 24, thereby performing cutting at thecutting reference position by the blade 24 (step S28). At this time, thecontrol unit 12 controls the incision depth of the blade 24 based on theZ coordinate of the cutting position P6.

Next, the control unit 12 repeats the steps S24 to S30 to sequentiallyform grooves G on the surface W_(S) of the workpiece W. When the cuttingat all the cutting positions has been completed (Yes in step S30), thegrooving of the workpiece W is terminated.

Note that in the present embodiment, the height at each position of thesurface W_(S) of the workpiece W is calculated to calculate thecoordinates of the vertex in the Z-axis direction of the workpiece W,but the presently disclosed subject matter is not limited to thismanner. For example, the coordinate of the vertex may be calculatedbased on an image obtained by measuring the surface W_(S) of theworkpiece W (for example, contrast, light amount, shading or the like).

FIG. 8 is a diagram for illustrating a procedure for detecting thevertex of the workpiece. (A) of FIG. 8 is a diagram showing thepositional relationship between the workpiece and the sensor unit, and(B) of FIG. 8 is a graph showing the change in contrast. In the exampleillustrated in FIG. 8, a case where the shape of the surface W_(S) ofthe workpiece W is a cylindrical (perfect circle) shape will bedescribed.

In the example illustrated in FIG. 8, the sensor unit 26 includes acamera having a focus lens and an imaging device (for example, a CCD(Charge Coupled Device)). When a vertex Pc (a point having the largest Zcoordinate, that is, a point nearest to the camera) on the surface W_(S)of the workpiece W is detected, the control unit 12 controls the focuslens of the camera of the sensor unit 26 to fix the focus lens in astate where the focus lens is focused on a point which is farther beyondthe vertex Pc of the surface W_(S) of the workpiece W.

Next, the control unit 12 controls the Y drive unit 20Y to move thecamera of the sensor unit 26 in the Y direction (the direction along athird axis) and capture an image. The control unit 12 detects the vertexbased on this image. In the example illustrated in (A) of FIG. 8, thecamera of the sensor unit 26 is focused on points FP1 and FP2 of thesurface W_(S) of the workpiece W at positions 26A and 26C, and is out offocus at positions 26B and 26D.

As illustrated in (B) of FIG. 8, a contrast value output from the cameraof the sensor unit 26 is maximized at the positions Y1 and Y2corresponding to the focusing positions FP1 and FP2 of the cameras,respectively. When the surface shape of the workpiece W is a cylindrical(perfect circle) shape, the Y coordinate Yc of the vertex Pc of theworkpiece W is Yc (=|Y2−Y1|/2) because the surface W_(S) of theworkpiece W is approximately line-symmetrical with respect to the Zaxis. With respect to the Z coordinate Zc of the vertex Pc, it may bemeasured by the focus function of the camera of the sensor unit 26, ormay be measured by using a displacement sensor. If the shape of thesurface W_(S) of the workpiece W is known in advance, it may becalculated from the surface shape.

Here, it is preferable in the vertex detection method illustrated inFIG. 8 that the depth of field is shallowed (for example, the focallength of the camera lens of the sensor unit 26 is increased or theaperture value (F value) of the camera lens of the sensor unit 26 isdecreased). As a result, the range in which the camera of the sensorunit 26 is in focus can be narrowed, so that the focusing positions FP1and FP2 can be detected with high accuracy.

In FIG. 8, the workpiece W whose surface W_(S) has the cylindrical(perfect circle) shape has been described. However, even when theworkpiece W has a non-cylindrical shape deviated from the cylindricalshape, it would be possible to detect the position of the vertex Pc bythe vertex detection method illustrated in FIG. 8 if the surface W_(S)is substantially line-symmetric with respect to the Z axis.

Further, even when the surface W_(S) is not substantiallyline-symmetrical with respect to the Z axis, it is possible to performvertex detection by using the vertex detection method illustrated inFIG. 8 and the detection using the displacement sensor in combination.For example, a position in the vicinity of a median line of the focusingpositions FP1 and FP2 is specified as an approximate position of thevertex Pc by the vertex detection method illustrated in FIG. 8, and anaccurate position of the vertex Pc is detected by using the displacementsensor, whereby the vertex detection can be efficiently performed.

Further, the position of the vertex may be calculated based on aphysical quantity other than the contrast value, for example, a changein light amount, shading or the like.

[When the Surface Shape of the Workpiece is not a Cylindrical (PerfectCircle) Shape]

In the above-described embodiment, the case where the shape of thesurface W_(S) of the workpiece W is a cylindrical (perfect circle) shapehas been described, but there is a case where the shape of the surfaceW_(S) of the workpiece W is deviated from the cylindrical (perfectcircle) shape depending on the accuracy in the bending processing of theworkpiece W (for example, the layer of the piezoelectric element).

FIG. 9 is a diagram showing an example in which the surface shape of theworkpiece is not a cylindrical shape. In FIG. 9, reference character Widesignates the surface of the workpiece W in the case of an idealcylindrical (perfect circle) shape. Here, for convenience ofillustration, the displacement of the workpiece W and the shape of thegroove are illustrated to be exaggerated.

In the example illustrated in FIG. 9, the surface W_(S) of the workpieceW is displaced to the −Z side with respect to the surface Wi having theideal cylindrical shape at the cutting position. Therefore, if groovingis performed on the assumption of the cylindrical-shape surface W1, theincision depth of the blade 24 shallows as designated by referencecharacter Gi. When the workpiece W is a layer of a piezoelectric elementhaving a drive electrode, it would be impossible to divide the driveelectrode if the incision depth of the blade 24 is insufficient.

Therefore, the actual height position in the Z direction of the cuttingposition is measured by the sensor unit 26, and further the difference dof the actual height position from that in the case of an idealcylindrical shape is measured by the calculating unit 16. When groovingof a groove Gs is performed, the control unit 12 performs cut-feeding sothat the blade 24 is located more deeply in the −Z direction by thedifference d.

On the contrary, when the surface W_(S) of the workpiece W is displacedto the +Z side at the cutting position, the cut-feeding is performed sothat the blade 24 is located more shallowly in the +Z direction. Inother words, in the above embodiment, it is possible to surely cut theworkpiece W by adjusting the depth of the cut-feeding of the blade 24based on a measurement result of the actual height position in the Zdirection of the cutting position.

[Specific Example of Grooving for an Outwardly-ConvexCurved-Surface-Shape Workpiece]

Next, a procedure of grooving for an outwardly-convexcurved-surface-shape workpiece will be described with reference to FIGS.10 to 17. FIGS. 10 to 17 are diagrams for illustrating the procedure ofgrooving for the outwardly-convex curved-surface-shape workpiece. Here.FIG. 13 is a partially enlarged view of FIG. 12 (an enlarged view of aportion of XIII).

In the following description, a case where grooves G are formed at equalintervals in the circumferential direction on the surface W_(S) of theworkpiece W will be described. Further, FIGS. 10 to 17 show theworkpiece W which is simplified as a fan shape connecting the surfaceW_(S) and the center thereof. Further, the position of the workpiecerotation axis (R-axis) is assumed to be set to the origin (Y, Z)=(0, 0).

(Procedure 1: Calculate the Surface Shape of the Workpiece)

First, the workpiece W is attached to the rotary table 28R, and theshape of the surface W_(S) of the workpiece W is calculated. In thepresent embodiment, a surface shape function Z=f(Y) indicating the shapeof the surface W_(S) of the workpiece W on the YZ plane is calculated.Note that in the present embodiment, when the workpiece W is attached tothe rotary table 28R the central axis of the workpiece W and theworkpiece rotation axis (R-axis) only need to be parallel to each other,and are not required to match each other.

As illustrated in FIG. 10, at least one alignment mark M1 indicating areference of the cutting position (cutting reference position) P₀ isformed on the surface W_(S) of the workpiece W. In the followingdescription, a position where the cutting reference position P₀ matchesthe vertex of the surface W_(S) of the workpiece W (the point where theZ coordinate is maximum) is defined as a reference rotation position W₀,and positions of the workpiece W when the workpiece W iscounterclockwise rotated by an angle φ (10° in one example), 2φ, 3φ, and4φ with respect to the reference rotation position W₀ are defined asrotation positions W₁, W₂, W₃, and W₄, respectively. The vertices of thesurface W_(S) of the workpiece W at the rotation positions W₁, W₂, W₃and W₄ are designated by Pc₁, Pc₂, Pc₃ and Pc₄, respectively.

Here, in the example illustrated in FIG. 10 and the like, the surfaceW_(S) of the workpiece W is illustrated as an ellipse, and referencecharacters C₀ to C₄ in the figures designate the positions of the centerof the surface W_(S) at the rotation positions W₀ to W₄, respectively.

When the surface shape function Z=f(Y) of the workpiece W is calculated,as illustrated in FIGS. 10 to 12, the control unit 12 counterclockwiserotates the workpiece W around the R-axis by each angle φ.

The detecting unit 14 scans the surface W_(S) of the workpiece W anddetermines the vertices Pc₁, Pc₂, Pc₃ and Pc₄ of the workpiece W at therespective rotation positions W₀, W, W₂, W₃ and W₄. As a result, asillustrated in FIG. 13, the coordinate (Y₀, Z₀) of the vertex (referencecutting position) P₀ at the reference rotation position W₀, and thecoordinates (Yc₁, Zc₁), (Yc₂, Zc₂), (Yc₃, Zc₃), and (Yc₄, Zc₄) of thevertices Pc₁, Pc₂, Pc₃ and Pc₄ of the workpiece W at the rotationpositions W₁, W₂, W₃ and W₄ to which the workpiece W is counterclockwiserotated by an angle φ, 2φ, 3φ, and 4φ with respect to the referencerotation position W₀ are calculated.

The calculating unit 16 calculates the coordinates (Ycr₁, Zcr₁), (Ycr₂,Zcr₂), (Ycr₃, Zcr₃), and (Ycr₄, Zcr₄) of points Pcr₁, Pcr₂, Pcr₃ andPcr₄ to which the vertexes Pc₁, Pc₂, Pc₃ and Pc₄ of the workpiece W atthe rotation positions W₀, W, W₂, W₃ and W₄ are clockwise rotated aroundthe R-axis by an angle φ, 2φ, 3φ, and 4φ, respectively. As illustratedin FIG. 14, when the workpiece W is located at the reference rotationposition W₀, the points Pcr₁, Pcr₂, Pcr₃ and Pcr₄ are located on thesurface W_(S) of the workpiece W.

Likewise, the control unit 12 detects a vertex by using the detectingunit 14 at each of rotation positions to which the workpiece W isrotated clockwise by an angle φ, 2φ, 3ρ, and 4φ respectively withrespect to the reference rotation position W₀. Further, the calculatingunit 16 calculates the coordinates of points Pcr⁻¹, Pcr⁻², Pcr⁻³, andPcr⁻⁴ to which these vertices are rotated counterclockwise by each angleφ. As a result, the coordinates of the points Pcr⁻⁴, Pcr⁻³, Pcr⁻²,Pcr⁻¹, P₀, Pcr₁, Pcr₂, Pcr₃ and Pcr₄ on the surface W_(S) of theworkpiece W at the reference rotation position W₀ are calculated.

The calculating unit 16 calculates the surface shape function Z=f(Y) ofthe workpiece W by using the coordinates of the points Pcr⁻⁴, Pcr⁻³,Pcr⁻², Pcr⁻¹, P₀, Pcr₁, Pcr₂, Pcr₃ and Pcr₄ on the surface W_(S) of theworkpiece W. Here, the surface shape function Z=f(Y) can be determined,for example, by using the coordinates of the points Pcr⁻⁴, Pcr⁻³, Pcr⁻²,Pcr⁻¹, P₀, Pcr₁, Pcr₂, Pcr₃ and Pcr₄ on the surface W_(S) of theworkpiece W, for example, according to polynomial interpolation,segmented polynomial interpolation, Lagrange interpolation, splineinterpolation, Newton interpolation or the like. Note that thecalculation method of the surface shape function Z=f(Y) is not limitedto this method, and for example, the least squares approximation may beapplied.

In the example illustrated in FIGS. 10 to 14, the number of rotationpositions at which vertices are detected for calculating the surfaceshape function Z=f(Y) is set to 9, but the presently disclosed subjectmatter is not limited to this number. The number of rotation positionscan be increased or decreased according to the required accuracy and thelike. Further, the angles for measuring a plurality of rotationpositions are not required to be equal to one another. For example, thenumber of vertices may be increased for portions (for example, portionsin the vicinity of both end portions in the Y direction) whose shapesare considered to be greatly deviated from the cylindrical shape.

Note that, in the present embodiment, the surface shape function Z=f(Y)is calculated based on the detection result of the coordinates of thevertices at a plurality of rotation positions, but the presentlydisclosed subject matter is not limited to this manner. For example, adisplacement sensor capable of scanning the entire surface W_(S) of theworkpiece W in the Y direction may be used as the sensor unit 26 tomeasure the shape of the surface W_(S) of the workpiece W and calculatethe surface shape function Z=f(Y) based on the measurement resultwithout detecting a vertex at each rotation position of the workpiece W.

(Procedure 2: Calculation of Cutting Position)

Next, the cutting position on the surface W_(S) of the workpiece W iscalculated based on the surface shape function Z=f(Y) of the workpieceW.

In the present embodiment, an example in which every five grooves oneach of the right and left sides of the reference cutting position P₀,that is, a total of eleven grooves G are formed at equal intervals(pitch P) as illustrated in FIG. 15 will be described. Note that thenumber of grooves G is not limited to this number. In the followingdescription, the cutting position on the right side of FIG. 15 withrespect to the reference cutting position P₀ is defined as P₁ to P₅ inorder from the P₀ side, and the cutting position on the left side ofFIG. 15 with respect to the reference cutting position P₀ is defined asP⁻¹ to P⁻⁵ in order from the P₀ side. Here, the cutting position P_(n)is a position which is displaced from the reference cutting position P₀to the right side (+Y side) by only a distance nP in FIG. 15 on thesurface shape function Z=f(Y), and the cutting position P_(−n) is aposition which is displaced from the reference cutting position P₀ tothe left side (−Y side) in FIG. 15 by only a distance nP on the surfaceshape function Z=f(Y) (n=1, . . . , 5).

The calculating unit 16 calculates the coordinates of the cuttingpositions P₁ to P₅ and P⁻¹ to P⁻⁵ when the workpiece W is located at thereference rotation position W₀. The distance P from the cutting positionP_(n-1) to P_(n) on the surface shape function Z=f(Y) is expressed bythe following equation (9). Here, f(Y) is a function obtained byperforming first derivation (partial differentiation) on the surfaceshape function Z=f(Y) with respect to Y.

$\begin{matrix}\left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack & \; \\{P = {\int_{P_{n - 1}}^{P_{n}}{\sqrt{1 + \left\lbrack {f^{\prime}(Y)} \right\rbrack^{2}}{dY}}}} & (9)\end{matrix}$

Y₁ is calculated by substituting the Y coordinate Y₀ of the cuttingreference position P₀ and the pitch P into the equation (9) with n=1 andsolving the equation (9) for the Y coordinate Y₁ of the cutting positionP₁. The Z coordinate Z₁ of the cutting position P₁ is calculated bysubstituting Y₁ into the surface shape function Z=f(Y).

Subsequently, the Y coordinate Y_(n) of the cutting position P_(n) iscalculated by substituting the Y coordinate Y_(n-1) of the cuttingposition P_(n-1) into the equation (9) and solving the equation (9), andthe Z coordinate Zn of the cutting position P_(n) is calculated bysubstituting Y_(n) into the surface shape function Z=f(Y). By repeatingthe above calculation, the coordinates of the cutting positions P₁ to P₅and P⁻¹ to P⁻⁵ when the workpiece W is located at the reference rotationposition W₀ are calculated.

When the interval (pitch P) of the grooves G is short, in other words,when the surface shape function Z=f(Y) between the cutting positionsP_(n-1) and P_(n) can be regarded as a straight line, it is possible todetermine the coordinate of the cutting position P_(n) by using thefollowing equation (10) and the surface shape function Z=f(Y).

[Expression 2]

P=√{square root over ((Y _(n) −Y _(n-1))²+(Z _(n) −Z _(n-1))²)}  (10)

Note that in the equation (9), the coordinate of the cutting positionP_(n) is calculated from the coordinate of the cutting position P_(n-1)adjacent thereto, but the presently disclosed subject matter is notlimited to this manner. For example, the coordinate of the cuttingposition P_(n) may be calculated from the coordinate of the referencecutting position P₀ by using the following equation (11).

[Expression 3]

nP=∫ _(P) ₀ ^(P) ^(n) √{square root over (1+[f′(Y)]²)}dY  (11)

In addition, in the present embodiment, the coordinate of the cuttingposition P_(n) is calculated based on the surface shape function Z=f(Y)and the interval (pitch P) of the grooves G, but the presently disclosedsubject matter is not limited to this manner. For example, when analignment mark indicating the cutting position P_(n) is formed inadvance on the surface of the workpiece W, the procedure 2 can beomitted.

(Procedure 3: Calculation of the Rotation Angle of the Workpiece DuringCutting)

As described above, in order to secure the processing accuracy (divisionaccuracy) of the workpiece W, the incision direction of the blade 24 isrequired to be perpendicular to the surface W_(S) of the workpiece W.Therefore, when cutting is performed at the cutting position P_(n), thecalculating unit 16 calculates the rotation angle δ_(n) (the rotationangle from the reference rotation position W₀) of the workpiece W atwhich the cutting position P_(n) matches the vertex of the workpiece W.When cutting is performed at the cutting position P_(n), the controlunit 12 rotates the workpiece W so that the cutting position P_(n)matches the vertex of the workpiece W.

By designating the normal line at the cutting position P_(n) by Ln whenthe workpiece W is located at the reference rotation position W₀, thegradient of the normal line Ln is equal to −1/f(Y_(n)). As illustratedin FIG. 16, when the intersection angle between the normal line Ln andthe Z-axis is designated by δ_(n), the following equation (12) isobtained. Here, for the sake of simplicity, only a normal line L₄ and anangle δ₄ are illustrated in FIG. 16.

$\begin{matrix}\left\lbrack {{Expression}\mspace{14mu} 4} \right\rbrack & \; \\{{\tan\left( {{90{^\circ}} - \delta_{n}} \right)} = {- \frac{1}{f^{\prime}\left( Y_{n} \right)}}} & (12)\end{matrix}$

As illustrated in FIG. 14, in order to match the cutting position P_(n)with the vertex of the surface W_(S) of the workpiece W, the workpiece Wmay be counterclockwise rotated from the reference rotation position W₀by δ_(n) so that the normal line L_(n) is parallel to the Z-axis. Bysolving the above equation (12), it is possible to calculate therotation angle δ_(n) from the reference rotation position W₀ to matchthe cutting position P_(n) with the vertex of the surface W_(S) of theworkpiece W.

Here, when the workpiece W is line-symmetrical with respect to theZ-axis at the reference rotation position W₀, |δ_(n)|=δ_(−n)|.

Further, in the present embodiment, the gradient of the normal lineL_(n) of the surface shape function Z=f(Y) at the cutting position P_(n)is calculated to make the normal line Ln parallel to the Z-axis.However, the gradient of the tangent line of the surface shape functionZ=f(Y) at the cutting position P_(n) may be calculated so that thetangent line is perpendicular to the Z-axis.

(Procedure 4: Calculation of the Coordinate of the Cutting PositionDuring Cutting)

Next, the coordinate of the cutting position P_(n) when the cuttingposition P_(n) is located at the vertex of the surface W_(S) of theworkpiece W is calculated. The coordinate of the cutting position P_(n)when the workpiece W is located at the reference rotation position W₀(before rotation) is designated by (Y_(n), Z_(n)), and the coordinate ofa cutting position Pr_(n) when the workpiece W is counterclockwiserotated from the reference rotation position W₀ by a rotation angleδ_(n) (after rotation) is designated by (Yr_(n), Zr_(n)). At this time,the coordinate (Yr_(n), Zr_(n)) of the cutting position Pr_(n) afterrotation is calculated by the following equations (13) and (14).

Yr _(n) =Y _(n)·cos δ_(n) −Z _(n)·sin δ_(n)  (13)

Zr _(n) =Y _(n)·sin δ_(n) +Z _(n)·cos δ_(n)  (14)

Note that in the present embodiment, the rotation angle δ_(n) of theworkpiece W is calculated based on the reference rotation position W₀,but it may be calculated based on another cutting position P_(n)(forexample, the cutting position P₅ or P⁻⁵ on the most ±Y side).

(Grooving)

Next, the control unit 12 controls the X drive unit 20X, the Y driveunit 20Y, the Z drive unit 20Z, and the R drive unit 20R to performgrooving. In the following description, for the sake of simplicity, itis assumed that the rotation position of the workpiece W at the starttime of grooving is the reference rotation position W₀, and the groovingis performed in the order of P₀, P₁, P₂, etc. Note that the order ofgrooving is not limited to this order. For example, P⁻⁵ is set to thevertex at the start time of grooving, and then the grooving may beperformed in the order of P⁻⁵, P⁻⁴, . . . , P₄, and P₅.

First, the control unit 12 performs grooving for the reference cuttingposition P₀ of the workpiece W while the workpiece W is located at thereference rotation position W₀. Here, the control unit 12 controls the Ydrive unit 20Y and the Z drive unit 20Z to perform alignment between theblade 24 and the reference cutting position P₀ (Y₀, Z₀) of the workpieceW. Then, the control unit 12 control the X drive unit 20X to performcut-feeding in the X direction of the workpiece table 30 whilecontrolling the Z drive unit 20Z to perform incision-feeding in the Zdirection of the blade 24, thereby performing cutting for the referencecutting position P₀ by the blade 24. At this time, the control unit 12controls the Z drive unit 20Z based on the Z coordinate Z₀ of thereference cutting position P₀ to control the incision depth of the blade24.

Next, when the grooving for the reference cutting position P₀ iscompleted, grooving for the cutting position P₁ (Pr₁) is performed. Thecontrol unit 12 controls the Z drive unit 20Z to retract the blade 24 inthe +Z direction. Thereafter, the control unit 12 controls the R driveunit 20R to counterclockwise rotate the workpiece W from the referencerotation position W₀ by only a rotation angle Si so that the cuttingposition P₁ (Y₁, Z₁) calculated in the procedures 1 and 2 is displacedto the vertex Pr₁ (Yr₁, Zr₁) of the workpiece W. As a result, the normalline Li of the surface shape function Z=f(Y) at the cutting position Pr₁(Yr₁, Zr₁) of the vertex of the workpiece W is parallel to the Z-axis.The control unit 12 performs grooving for the cutting position Pr₁ (Yr₁,Zr₁) as in the case of the reference cutting position P₀.

Next, when the grooving at the cutting position Pr₁ is completed,grooving is performed for the cutting position P₂ (Pr₂). The controlunit 12 retracts the blade 24, further counterclockwise rotates theworkpiece W by only a rotation angle (δ₂-δ₁), and then performs groovingfor the cutting position Pr₂ (Yr₂, Zr₂) in the same manner as describedabove.

The above procedure is subsequently repeated, whereby the grooving forthe cutting positions P₁ to P₅ and P⁻¹ to P⁻⁵ (Pr₁ to Pr₅ and Pr⁻¹ toPr⁻⁵) is completed.

According to the present embodiment, even when the surface W_(S) of theworkpiece W has a non-cylindrical shape, the incision direction of theblade 24 can be set to be perpendicular to the surface W_(S) of theworkpiece W by calculating the surface shape function Z=f(Y). As aresult, it is possible to adjust the incision position of the blade 24with high accuracy.

According to the present embodiment, since it is not necessary to makethe central axis of the workpiece W and the R-axis match each other, thedegree of freedom in the position and posture when fixing the workpieceW to the rotary table 28R is increased. Therefore, even in the case of alarge-size workpiece or an elongated workpiece, by adjusting theattachment position and posture of the workpiece W according to the sizeand shape of the workpiece W, it is possible to attach the workpiece Wso that the workpiece W can be fit in a space between the blade 24 andthe R-axis.

Note that, in the present embodiment, the case where the intervals ofthe grooves G on the surface W_(S) of the workpiece W are equal to oneanother has been described, but the presently disclosed subject matteris not limited to this manner. For example, even when the intervals ofthe grooves G are unequal to one another, the cutting position can becalculated by using the function of the surface W_(S) of the workpieceW. Therefore, the workpiece processing method according to theabove-mentioned embodiment can be applied to even a case where theintervals of the grooves G are unequal to one another.

[Workpiece Processing Method for Non-Cylindrical-Shape Workpiece]

Next, a workpiece processing method (grooving method) for anon-cylindrical-shape workpiece will be described with reference to FIG.18.

First, the workpiece W is carried into the workpiece processing device1, and fixed to the rotary table 28R (step S10).

Next, the control unit 12 calculates the surface shape function Z=f(Y)representing the shape of the surface W_(S) of the workpiece W (stepS102). In step S102, the control unit 12 controls the R drive unit 20Rto rotate the workpiece W, and measures the surface W_(S) of theworkpiece W by using a camera (see FIG. 8) of the sensor unit 26 at aplurality of rotation positions (see W₀ to W₄ in FIGS. 10 to 14). Thedetecting unit 14 uses data of a measurement result by the sensor unit26 to calculate the coordinates of the vertices (see P₀ of FIG. 13, Pcr₁to Pcr₄ and Pcr⁻¹ to Pcr⁻⁴) of the workpiece W from the rotationposition W₀ to the rotation position W₄. The calculating unit 16calculates the surface shape function Z=f(Y) based on the vertices ofthe workpiece W at the respective rotation positions (see FIGS. 10 to14). Here, in step S102, the surface shape function Z=f(Y) may bedirectly determined by using a sensor capable of measuring the Zcoordinate of the surface W_(S) of the workpiece W.

Next, the calculating unit 16 calculates the coordinate (Y_(n), Z_(n))of the cutting position P_(n) on the surface W_(S) of the workpiece Wbased on the surface shape function Z=f(Y) of the workpiece W and theinterval of the grooves G formed on the surface W_(S) of the workpiece W(step S104).

Next, the calculating unit 16 calculates the rotation angle Sn of theworkpiece W when the cutting position P_(n) (Y_(n), Z_(n)) matches thevertex of the workpiece W (step S106). Then, the calculating unit 16calculates the coordinate (Yr_(n), Zr_(n)) of the cutting position Prnwhen the workpiece W is rotated so that the cutting position P_(n)(Y_(n), Z_(n)) matches the vertex of the workpiece W (step S108).

Next, the control unit 12 controls the X drive unit 20X, the Y driveunit 20Y, the Z drive unit 20Z, and the R drive unit 20R to performgrooving (step S110: grooving step). Thereafter, the control unit 12repeats the step of grooving in step 110 to sequentially form thegrooves G on the surface W_(S) of the workpiece W.

Note that, in the above embodiment, the case where the shape of thesurface of the workpiece does not become a perfect circle shape due tothe accuracy at the time of bending has been described, but theapplication range of the presently disclosed subject matter is notlimited to workpieces whose shapes are deviated from the perfect circleshape. The presently disclosed subject matter can be applied to groovingon workpieces each having a curved surface shape that is convex on theoutside (+Z side).

REFERENCE SIGNS LIST

1 . . . work processing device, 10 . . . control device, 12 . . .control unit, 14 . . . detecting unit, 16 . . . calculating unit, 18 . .. input/output unit, 20X . . . X drive unit, 20Y . . . Y drive unit, 20Z. . . Z drive unit, 20R . . . R drive unit. 22 . . . cutting unit, 24 .. . blade, 26 . . . sensor unit, 28 . . . workpiece supporting unit, 28R. . . rotary table, 30 . . . workpiece table

1. A workpiece processing method for processing a workpiece having anoutwardly-convex curved-surface-shape surface that is non-cylindricalshape surface, comprising: a step of supporting the workpiece on aworkpiece supporting unit so that the workpiece is rotatable around afirst axis; a step of measuring the surface of the workpiece by a sensorunit; a step of calculating a surface shape of the workpiece on a planeperpendicular to the first axis based on a measurement result of thesurface of the workpiece; and a grooving step of rotating the workpiecearound the first axis based on the surface shape of the workpiece and acutting position at which a groove is formed on the surface of theworkpiece so that the cutting position matches a vertex in a directionalong a second axis which is perpendicular to the first axis andparallel to the blade, and relatively moving the workpiece supportingunit and the cutting unit, thereby forming a groove at the cuttingposition.
 2. The workpiece processing method according to claim 1,further including a step of calculating a normal line to the surface ofthe workpiece at the cutting position based on the surface shape of theworkpiece, and the grooving step including rotating the workpiece aroundthe first axis so that the normal line is parallel to a direction alonga second axis which is perpendicular to the first axis and parallel tothe blade, and relatively moving the workpiece supporting unit and thecutting unit, thereby forming a groove at the cutting position.
 3. Theworkpiece processing method according to claim 1, further including astep of calculating a tangent line to the surface of the workpiece atthe cutting position based on the surface shape of the workpiece, andthe grooving step including rotating the workpiece around the first axisso that the tangent line is perpendicular to a direction along a secondaxis which is perpendicular to the first axis and parallel to the blade,and relatively moving the workpiece supporting unit and the cuttingunit, thereby forming a groove at the cutting position.